Jacob Sapf was sitting across from the man and said he was “getting crazy” even before he got on the bus.

“He was approaching people, yelling at them, and somehow they let him on the bus anyway,” Sapf said.

Greyhound issued the following statement:

Thank you for your inquiry regarding the incident that occurred on Greyhound bus schedule #4921 headed from Milwaukee to Chicago with 17 passengers onboard. Safety is a cornerstone of our business and we treat any threat towards our passengers and/or employees seriously. We are fully cooperating with local law enforcement as they complete their investigation.

State police said a bomb dog arrived and conducted a sweep of the bus with negative results.